Work proposed for the coming year includes 1) a continuation of the analysis of maternal-effect mutations on the development of the axolotl, 2) additional work on the mode of action of a gene (e) causing eyelessness, also in the axolotl, and 3) transplantation of reticulocyte nuclei into activated eggs of the frog and the axolotl. The maternal effect mutation which has received and will receive most attention is that of the o gene. Females homozygous for this gene produce eggs which develop normally through cleavage, but are invariably blocked in gastrulation. A detailed analysis of the gastrulation block will be undertaken. The gene for eyelessness (e) leads to a complete failure of formation of the optic vesicles. Preliminary evidence indicates that the gene operates on the ectoderm overlying the forebrain, conferring on it a specific inhibitory effect on the differentiation of the eye. Work is planned to consolidate and expand the evidence on this point. The reticulocyte transplantation work is being planned for the purpose of determining why these nuclei promote development only to an advanced tailbud stage. Work planned will include chromosome studies and tests of transcriptional activity on the part of the transplanted nuclei.